DE8700885U1 - Probe for coordinate measuring machines - Google Patents

Description

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Description: Company Carl Zeisa

7920 Heidenheim Probe for coordinate measuring machines

Probe heads for coordinate measuring machines have a movable part that carries the probe pin and the probe ball, which is deflected from the rest position against the force of one or more springs, usually spiral springs, during each probing process. This deflection movement is necessary to protect the probe head from being destroyed as a result of the coordinate measuring machine inevitably overrunning the probing position. Probe heads for coordinate measuring machines are described, for example, in DE-PS 23 47 633 and DE-OS 27 43 665.

When designing probe heads, the greatest possible free stroke for the probe deflection is required, so that high travel speeds and short measuring times can be achieved. On the other hand, the probe head should be structurally kept as small as possible so that even hard-to-reach areas on the workpiece can be probed.

Fulfilling both requirements at the same time is particularly difficult when cables have to be routed to the moving part of the probe. This is necessary, for example, with probes that have a piezoelectric oscillator, such as the pressure-sensitive sensors described in DE-PS 27 12 181 or the probe described in international application WO 81/01876, and these electrical components are attached to the moving part itself. This is because continuous large deflection movements in a very small space pose the risk of cable breakage. In addition, the cable itself creates additional reset forces, which reduces the measurement accuracy that can be achieved with the probe or even completely disrupts the function of the probe.

Although it is known to lay cables in loops, the load on the cable when the cables move

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The innovation is based on the task of routing the cable connection between the moving part and the fixed part of a probe for coordinate measuring devices in the smallest possible space so that even with large deflections of the probe pin, the cable stress is as low as possible.

This task is solved according to the measures specified in the characterizing part of the main claim in that the cables are attached to the spring (5) following the windings of the spring. Particularly good results are obtained when the cables are wound around the spring wire.

Because of the spring wrap, the movements of the cables are evenly distributed over their entire length, so that the restoring forces they exert on the stylus remain minimal even in the event of extreme deflections. At the same time, the cables are fixed along their entire length between the movable and the rigid part of the probe head and cannot shift in an undefined manner.

An example of the innovation is described below using the attached drawing: In the only figure, (1) indicates the housing of the probe, which is attached to a coordinate measuring machine (not shown here). In the housing (1), which is the fixed part of the probe, there is a bearing made up of three balls, onto which the carrier plate (2) for the probe pin (3) and the probe ball (4) is pressed by a spiral spring (5). In the illustration shown, only two of the three balls of the bearing are visible, namely the balls (7a) and (7b).

The deflection of the stylus (3) from the bearings

The carrier plate (2) that lifts the balls (7) is split in two and is provided with a piezoelectric sensor (8) that supplies the contact signal. A cable connection consisting of two cables (6a and 6b) leads from the sensor (8) to a socket (not shown here) at the upper end of the housing (1).

The cables are wound around the spring wire following the turns of the spring (5) and are thus attached to the spring (5) along its entire length. This means that the loads acting on the cables are evenly distributed over their entire length each time the stylus (3) is deflected.

It is clear that in this way not only the moving part in the probe itself, but also other bends on coordinate measuring machines, e.g. a flexible holder for the complete probe that serves as collision protection, can be designed according to the innovation.

Claims (2)

&bull; ■ Mil Protection Claims: 87002 G 1. Probe head for coordinate measuring machines with a movable part (2) carrying the probe pin (3), which can be deflected against the force of one or more springs (5), and a cable connection (6) between the movable part (2) and the fixed part (1) of the probe head, characterized in that the cables (Aa, 6b) correspond to the windings of the Spring (5) is attached to it. 2. Tag head for coordinate measuring machines according to claim 1, characterized in that the cables are wound around the spring wire.